SILVER NANOTECHNOLOGIES AND THE ENVIRONMENT: OLD PROBLEMS OR NEW CHALLENGES? doc

Project on Emerging Nanotechnologies Project on Emerging Nanotechnologies is supported by THE PEW CHARITABLE TRUSTS One Woodrow Wilson Plaza 1300 Pennsylvania Ave., N.W. Washington, DC 20004-3027 T 202.691.4000 F 202.691.4001 www.wilsoncenter.org/nano www.nanotechproject.org PEN 15 SEPTEMBER 2008 The Project on Emerging Nanotechnologies Samuel N. Luoma OLD PROBLEMS OR NEW CHALLENGES? SILVER NANOTECHNOLOGIES AND THE ENVIRONMENT: WOODROW WILSON INTERNATIONAL CENTER FOR SCHOLARS Lee H. Hamilton, President and Director BOARD OF TRUSTEES Joseph B. Gildenhorn, Chair David A. Metzner, Vice Chair PUBLIC MEMBERS James H. Billington, The Librarian of Congress; Bruce Cole, Chairman, National Endowment for the Humanities; Michael O. Leavitt, The Secretary, U.S. Department of Health and Human Services; Tami Longabergr, Designated Appointee within the Federal Government; Condoleezza Rice, The Secretary, U.S. Department of State; G. Wayne Claugh, The Secretary, Smithsonian Institution; Margaret Spellings, The Secretary, U.S. Department of Education; Allen Weinstein, Archivist of the United States PRIVATE CITIZEN MEMBERS Robin B. Cook, Donald E. Garcia, Bruce S. Gelb, Sander R. Gerber, Charles L. Glazer, Susan Hutchison, Ignacio E. Sanchez The PROJECT ON EMERGING NANOTECHNOLOGIES was launched in 2005 by the Wilson Center and The Pew Charitable Trusts. It is dedicated to helping business, governments, and the public anticipate and manage the possible human and environmental implications of nanotechnology. THE PEW CHARITABLE TRUSTS serves the public interest by providing information, advancing policy solutions and supporting civic life. Based in Philadelphia, with an office in Washington, D.C., the Trusts will invest $248 million in fiscal year 2007 to provide organ- izations and citizens with fact-based research and practical solutions for challenging issues. www.pewtrusts.org The WOODROW WILSON INTERNATIONAL CENTER FOR SCHOLARS is the living, national memo- rial to President Wilson established by Congress in 1968 and headquartered in Washington, D.C. The Center establishes and maintains a neutral forum for free, open and informed dialogue. It is a nonpar tisan institution, suppor ted by public and private funds and engaged in the study of national and international affairs. ILLUSTRATIONS BY Jeanne DiLeo TTAABBLLEE OOFF CCOONNTTEENNTTSS FOREWORD ABOUT THE AUTHOR EXECUTIVE SUMMARY I. INTRODUCTION II. FATE AND EFFECTS OF SILVER IN THE ENVIRONMENT History of Silver Toxicity Source-Pathway-Receptor-Impact Sources: How Much Silver Is Released to the Environment by Human Activities? Pathways: What Are the Concentrations of Silver in the Environment? Pathways: Forms and Fate Receptor: In What Forms Is Silver Bioavailable? Impact: Toxicity of Silver III. EMERGING TECHNOLOGIES AND NANOSIL VER Conceptual Framework Sources of Nanosilver and Potential Dispersal to the Environment Mass Discharges to the Environment from New Technologies Pathways of Nanosilver in the Environment Is Nanosilver Bioavailable? How Does Nanosilver Manifest Its Toxicity? IV . THE W A Y FORWARD: CONCLUSIONS AND RECOMMENDATIONS 1 4 5 9 14 14 14 15 18 20 22 25 35 35 35 39 44 47 51 57 The opinions expressed in this repor t are those of the author and do not necessar il y reflect views of the W oodrow Wilson Inter national Center for Scholars or The Pew Charitable Trusts. Samuel N. Luoma PEN 15 SEPTEMBER 2008 OLD PROBLEMS OR NEW CHALLENGES? SILVER NANOTECHNOLOGIES AND THE ENVIRONMENT: [...]... addresses the unique implications of using and releasing silver in nanoparticle form The report concludes with recommendations for next steps 13 14 II FATE AND EFFECTS OF SILVER IN THE ENVIRONMENT HISTORY OF SILVER TOXICITY One of the important uncertainties about nanosilver technologies is the contradiction between the long history of intimate human use of silver and its classification as a persistent and. .. even the most contaminated open waters during the period of greatest silver contamination (Figure 4), which is another contradiction in the silver story PATHWAYS: FORMS AND FATE The form of silver in water is governed by the complex chemistry of the element and the nature of the water Silver is among the met- FIGURE 4 SILVER CONCENTRATIONS IN DIFFERENT WATERS GRAPHED ON A LOG SCALE 100000 33400 Silver. .. transporting amino acids and clusters of molecules of colloidal size, termed micelles Silver will accompany these molecules as they are transported into the cells of the organism Similarly, mechanisms exist to engulf particles and either digest them within the cell (intracellular digestion) or transport them through the membrane (endocytosis) In the past decade researchers have quantified the importance... all the local POTWs around the South Bay, as they were nationally, during the 1980s and 1990s Probably more important, silver recycling was initiated for local industries, and the use of silver in photography declined considerably The mass of silver released to South Bay in the wastes declined more than tenfold as a result of these changes In 2006, when silver releases were 6 kg per year, inputs to the. .. transported by a carrier system that controls the cell’s concentration of sodium and/ or copper (Bury and Wood, 1999) Silver uptake by the transporters (its bioavailability) is strongly influenced by the form of silver in the environment One form favored for uptake by the transporters is ionic silver (Ag+), because its properties are most similar to those of sodium (Na+) and copper, which is transported... constants, define the strength of each metal-ligand complex These constants can be used in models to predict silver speciation in solution or distribution among ligands Speciation is driven by the combination of: a) The strength of silver association with the ligand (if silver associates more strongly with one ligand than another, it is more likely to associate with the first); and These properties work in combination... gills or ingesting food, sediments or suspended material Bioavailability is the sum of silver taken up from all these sources Silver must penetrate the tissues of an organism before it can be toxic, so the bioaccumulated concentration is an indicator of the dose of silver to which an organism has been exposed The biological systems that transport materials across the boundary between an organism and. .. world (e.g., Europe, North America, Japan, Australia and New Zealand) After the 1980s, emissions began to decline in these jurisdictions with the passage and implementation of environmental legislation such as like the Clean Water Act in the USA in the 1970s Industries and cities were forced to remove or capture contaminant materials, including silver, preventing their disposal to the atmosphere and. .. ligand This distribution of silver between its ionic (Ag+) and its ligand-bound forms is termed speciation Silver forms especially strong complexes with free sulfide (-SH) ligands, and with the sulfide ligands that occur within organic materials dissolved in natural waters (Adams and Kramer, 1999) It is possible for dissolved sulfide and/ or organic matter to complex essentially all the dissolved silver. .. Well-documented examples also exist where silver contamination in water and mud corresponds strongly with ecological damage to the environment (Hornberger et al., 2000; Brown et al., 2003) SOURCE-PATHWAY-RECEPTOR-IMPACT The complex behavior of silver contributes to the contradictory conclusions about its effects on human health and the environment: • Different uses release silver in different forms and . 202.691.4001 www.wilsoncenter.org/nano www.nanotechproject.org PEN 15 SEPTEMBER 2008 The Project on Emerging Nanotechnologies Samuel N. Luoma OLD PROBLEMS OR NEW CHALLENGES? SILVER NANOTECHNOLOGIES AND THE ENVIRONMENT: WOODROW. Regardless of the scope of the nanosilver problem, it underscores the need for new approaches to oversight to deal with the new technologies and problems of the new century. Laws and institutions. priorities. That is the major policy issue. However, there is also a need for surveillance and reporting. Workers, consumers, lakes and streams are being exposed to nanosilver and, while the